1. Field of the Invention
This invention relates generally to rheometers and more particularly to on-line rheometers that provide analysis of the viscosity of a product, particularly such as a foamable plastics product, in a manner adaptable to computer control to optimize manufacturing conditions. During the manufacture of a foamable plastics material, such as polystyrene, there is a good deal of waste which is in turn chopped up for recycling and mixing with virgin material. Since the viscosity of recycled material varies, it also introduces variations in the viscosity of the foamable resin mix, leading to difficulty in producing uniform foam products. Thus, the viscosity must be continuously measured and controlled. The viscosity of resin mix may be controlled by the percentage of recycled material, the percentage of blowing agent and/or the melt temperature.
2. Description of the Prior Art
Rheometers, including rheometers that employ a restriction such as a slit or a capillary, are well known. Of special interest is U.S. Pat. No. 4,241,602 to C. D. Han and prior art identified therein, all of which is hereby specifically incorporated by reference.